1. Field of the Invention
The present invention relates to a method for forming a semiconductor film utilizing the chemical vapor deposition (CVD) method and in particular relates to a method for forming a semiconductor film utilizing a catalytic chemical vapor deposition (CVD) method for forming deposits of activated gas material by means of a catalytic piece and also to a manufacturing method for semiconductor devices utilizing this forming method.
2. Description of Related Art
In the typically used method for growing an epitaxial film of silicon, a silicon substrate is heated to a temperature of approximately 700xc2x0 C. to 1200xc2x0 C. and gas material such as silane, dichlorosilane, trichlorosilare and silicon tetrachloride made to react and breakdown in a hydrogen atmosphere, at 100 to 760 Torr.
The silicon film obtained by this kind of epitaxial growth is subjected to submicron processing by lithographic technology or etching technology and patterned in the desired configuration in order to utilize the silicon film for instance as logic gates or interconnections in semiconductor devices.
However, increasing demands are being made for lower cost and improved productivity so that simplifying and reducing the steps in this process has also become necessary.
In view of this situation, when forming the above mentioned silicon film, rather than performing patterning after developing the epitaxial film, a better approach is to selectively develop the epitaxial film and eliminate the silicon film patterning process.
More specifically, when growing an epitaxial film of silicon, a mask of silicon oxide having an aperture is formed on the silicon substrate. Hydrogen chloride gas is then mixed into the gas material and a vapor reaction made to occur by methods such as heat chemical vapor deposition (CVD) so that epitaxial silicon is selectively developed only on the silicon substrate surface within the aperture exposed by the mask, and the depositing of polysilicon film on the silicon oxide can be prevented. Preventing the deposit of silicon onto the surface of the silicon oxide film is possible because the hydrogen chloride gas mixed into the gas material becomes activated and etches away the surface of the oxide silicon film.
However, in this method using hydrogen chloride gas mixed into the gas material, the hydrogen chloride breaks down, and the chloride that is formed pollutes the inside of the reaction chamber so that maintenance (cleaning) of the processing equipment is required, thus creating the disadvantage that time is required for cleaning.
Also since this method uses hydrogen chloride gas mixed in with the gas material, the energy causing a chemical reaction from the gas material, and the energy causing epitaxial growth (single crystalline growth) of the generated silicon onto the surface of the silicon substrate, are all supplied in the form of heat energy to the silicon substrate from the heater installed on the substrate holder (susceptor). The temperature of the silicon substrate warmed by the heater or in other words, the epitaxial temperature cannot be greatly reduced from approximately 700xc2x0 C., which in turn places large restrictions on the selection of material forming this substrate and the elements formed on this substrate.
A further disadvantage of this method is that since the heating temperature of the silicon substrate cannot be reduced when for instance, the basic elements on the substrate are polysilicon diffused with impurities, these impurities might possibly re-diffuse in the silicon during the process.
In view of the;above described problems with the related art, this invention therefore has the object of providing a method for forming a semiconductor film, that allows easy cleaning of the processing equipment and is capable of forming an epitaxial film at low temperatures as well as a manufacturing method for semiconductor devices until zing this forming method to achieve selective crystalline growth of semiconductor film.
As a means to eliminate the above described problems, the method for forming a semiconductor film of this invention comprises a process for forming a mask having an aperture exposing the substrate surface on the substrate, and a process for forming a semiconductor film by selective crystalline growth on a semiconductor piece by means of catalytic chemical vapor deposition (CVD) on the substrate surface exposed by an aperture on the mask. this forming method, a mask is formed of at least one type from among silicon oxide, silicon nitride, or silicon oxygen-nitride on a semiconductor piece, and by heat breakdown and activation with a catalytic piece if performing catalytic chemical vapor deposition (CVD) using hydrogen gas, selective etching is performed using gas material having clusters of high energy hydrogen atoms or hydrogen molecules, so that silicon is not deposited on the mask at a certain time yet crystalline growth is made to selectively occur on the substrate.
In the CVD method, the high energy to cause the gas material to chemically react is basically supplied by the catalytic piece, and just an amount of energy necessary to develop the epitaxial film (single crystalline growth) on the substrate surface of the silicon, or in other words just an amount of energy needed to align the silicon atoms in the direction of crystallization on the substrate surface is applied, so that the heating temperature of the substrate itself can be a low temperature of for instance, 100xc2x0 C. to 700xc2x0 C.
To further, eliminate the above described problems, the manufacturing method for semiconductor devices of this invention comprises a process for forming a mask having an aperture exposing the substrate surface on the substrate, and a process for forming a semiconductor film by selective crystalline growth on a semiconductor piece by means of catalytic chemical vapor deposition (CVD) on the substrate surface exposed by an aperture on the mask, and a process for performing a specified processing on the semiconductor film and form semiconductor devices.
By performing the specified processing on the semiconductor film obtained by the above described semiconductor film forming method, and forming semiconductor devices by the manufacturing method for semiconductor film of this invention, the above described effects are obtained so selective crystalline growth of semiconductor film on the substrate surface can be performed at low temperatures.